The present invention relates to an atomic absorption spectrophotometer, and more particularly to a small-sized atomic absorption spectrophotometer comprising either a graphite furnace analyzing section or a flame analyzing section, or comprising both of them.
Atomic absorption spectrophotometers are generally used for the quantitative analysis of metal including heavy metals, it is well-known that the spectrophotometers is used for the following analysis methods. In the flame analyzing method, a sample including metal to be analyzed is sprayed into combustion flame such as acetylene flame to atomize the sample. A luminous flux having a wavelength which is absorbed by the metal to be analyzed is passed through the flame. Detecting attenuation of the luminous flux, the quantity of the metal included in the sample is detected. In the graphite furnace analyzing method, a sample is dropped into a heated graphite pipe to vaporize and atomize the sample. And then, same as above-mentioned method, a luminous flux having a wavelength which is absorbed by the metal to be analyzed is passed through the graphite pipe. Detecting attenuation of the luminous flux, the quantity of the metal included in the sample is detected.
Concerning the kinds of metals which can be analyzed, there is a different territory between the flame analyzing method and the graphite furnace analyzing method. And lengths of time required for the analyses also differ between both of the methods. Therefore, generally, the atomic absorption spectrophotometers are so devised that analyses by both of the methods are possible.
FIG. 13 is a perspective view illustrating a configuration of an atomic absorption spectrophotometer according to the prior art. FIG. 14 is a diagram illustrating a state inside a lamp chamber. In FIGS. 13 and 14, reference numeral 1 denotes a main unit; reference numeral 2 denotes a lamp chamber; reference numeral 3 denotes a graphite furnace analyzing section; reference numeral 4 denotes a flame analyzing section; reference numeral 5 denotes an electric control section; reference numeral 6 denotes an autosampler; reference numeral 7 denotes a graphite furnace power supply section; reference numeral 8 denotes a cooling drain pot; reference numeral 21 denotes a door; reference numeral 22 denotes a switch; reference numeral 23 denotes an indicator; reference numeral 76 denotes lamps; and reference numeral 77 denotes a lamp holder.
As shown in FIG. 13, inside the main unit 1 of the atomic absorption spectrophotometer according to the prior art, the lamp chamber 2 equipped with the door 21 having a clear window is placed on the right side. The graphite furnace analyzing section 3 to which the autosampler 6 is connected, the flame analyzing section 4, and the electric control section 5 are sequentially placed in the left direction from a position next to the lamp chamber 2. The graphite furnace power supply section 7 is placed behind them. The autosampler 6 is a device by which using a micropipette. A sample to be analyzed is automatically dropped into a cylindrical heater made of graphite, which is called a cuvette of the graphite furnace analyzing section 3. Using the autosampler 6, it becomes possible to automatically and successively analyze a large number of samples.
In the example shown in FIG. 13, in the lower part of the flame analyzing section 4, a device for blowing a sample into the flame analyzing section 4 is provided at a position of the door opening downward. The flame analyzing section 4 can also be provided with an autosampler having the same functions as above although such an autosampler is not illustrated in the figure. Moreover, the whole atomic absorption spectrophotometer according to the prior art is controlled and operated by a personal computer, which is installed next to the main unit 1.
The door 21, the switch 22, the indicator 23 etc. are placed on the front of the lamp chamber 2. The door 21 is equipped with a clear window. Operating states of the hollow cathode lamps 76 placed inside, and the like, can be checked through the window.
As shown in FIG. 14, the plural hollow cathode lamps 76, which are attached to the turret-type lamp holder 77, are placed in the lamp chamber 2. Each of the hollow cathode lamps 76 corresponds to a metallic atom to be detected. The hollow cathode lamps 76 are attached to the lamp holder 77 perpendicularly, that is to say, in the vertical direction so that the hollow cathode lamps 76 are replaceable and their emission surfaces of luminous flux face upward. One of the hollow cathode lamps 76 required is positioned to a given position by rotating the lamp holder 77. The luminous flux from this hollow cathode lamp 76 is passed through various kinds of optical systems (not illustrated), and is further passed through the graphite furnace analyzing section 3, and the flame analyzing section 4. It finally reaches to a photomultiplier, and is converted into an electric signal. After that, a personal computer (not illustrated) placed next to the main unit 1 executes the quantitative analysis of target metal. With the door 21 of the lamp chamber 2 being opened, the hollow cathode lamp 76 is replaced.
The cooling drain pot 8, which is used for coolant such as water for cooling units inside the atomic absorption spectrophotometer, is provided on the left surface of the main unit 1.
In the atomic absorption spectrophotometer according to the prior art as described above, the plural hollow cathode lamps 76 (in the case of the example shown in FIG. 14, eight hollow cathode lamps 76) are attached to the lamp holder 77 that is rotatable. Positioning one of them to a given position makes it possible to analyze metal corresponding to the positioned lamp. Accordingly, it is possible to analyze eight kinds of metals successively and continuously without replacing the lamps. Moreover, it becomes possible to analyze many kinds of metals by replacing the hollow cathode lamps 76.
Incidentally, the prior art relating to the atomic absorption spectrophotometer as described above is known, for example, by the technology described in Japanese Patent Application Laid-Open No. Hei 10-73536, and others.
The atomic absorption spectrophotometer according to the prior art is configured as a tandem machine comprising the flame analyzing section and the graphite furnace analyzing section. In addition, the power unit, and the like, is placed behind the analyzing sections. Therefore, since its width and depth are large, a large area for installing the spectrophotometer has been required.
In addition, as for the above-mentioned prior art, if a special-purpose machine having only either the flame analyzing section or the graphite furnace analyzing section is required, the special-purpose machine is configured by utilizing the main unit that can be used in common. In this case, an unnecessary analyzing section is covered by a lid, or the like. Therefore, even if the Spectrophotometer is used as a special-purpose machine for flame analysis or a special-purpose machine for graphite furnace analysis, its dimensions cannot be reduced. Accordingly, if the machine is placed on the laboratory table in a laboratory, or the like, it protrudes from there.
Moreover, if an atomic absorption spectrophotometer comprising a graphite furnace analyzing section is configured, it is necessary to inject a sample into an atomization furnace with accuracy. In this case, as a general rule, the sample injection is automated by the autosampler. However, the atomic absorption spectrophotometer according to the prior art uses an autosampler of the rotary method that is difficult to adjust. Further, the autosampler protrudes forward from the front surface of the atomic absorption spectrophotometer. Therefore, when placing the atomic absorption spectrophotometer on a table, there is a high possibility that the autosampler will extend off the table into a passageway. Thereby, it is possible that people or something carelessly hit or touch the autosampler requiring a high degree of accuracy. Furthermore, because the autosampler is often placed in the front part of the graphite furnace, the autosampler becomes an obstacle to maintenance of the graphite furnace, making it difficult to perform maintenance work.